Require payment recreate when payment price is wrong

[orzechdev]

I want to merge this change because... it

• redirects the user to shipping step if payment amount is not equal to checkout total price (e.g. item was added to the cart) and thanks to it payment may be recreated with proper payment amount
• still preserves the possibility for user to go to payment step when shipping was set already
• fixes the case when user removes all items requiring shipping, leaving only digital product, when active path was /checkout/shipping and user was not redirected to other possible step
• fixes the case when user removes all items requiring shipping, leaving only digital product and shipping method was still wrongly set, while it shouldn't exist anymore and total price should be updated
• shipping method is now updated after adding/removing item to cart, and together with updated shipping methods introduced in Fix checkout refreshing #865, it is going to fix shipping method and payment gateway amount not updating when cart changes during checkout #885.

⚠️ Before merge SDK dependency must be updated with changes introduced in saleor/saleor-sdk#33

Screenshots

Pull Request Checklist

1. All visible strings are translated with proper context.
2. All data-formatting is locale-aware (dates, numbers, and so on).
3. The changes are tested.
4. The code is documented (docstrings, project documentation).
5. Changes are mentioned in the changelog.

Test Environment Config

API_URI=https://master.staging.saleor.rocks/graphql/

[patrys]

Task linked: SALEOR-623 Fix checkout flow when adding new product for order in review

[krzysztofwolski]

If you want to test it you have to mock the whole payment object and total price. I see 2 solutions:

1. Prefereble, easier to implement: Don't we have util for comparing prices?
   If not, I would suggest creating utils/money.ts file with such function (having all utils in one file leads to one, too long file with too broad scope - nightmare to work with).
   Also, unit tests for such function is a must.
2. Function isCheckoutFullyPaid which takes Checkout as an argument and performs needed checks. Thats more to mock, but could be easier to use in checkout views.

[orzechdev]

I have created isPriceEqual util

[tommytobi]

Another way to do it could be to update the available shipping methods when the cart is updated, then check the id of the available shipping methods against the id of the chosen shipping method in the checkout router.